where \(\delta \)  is a phase that includes dynamical contributions due to the energy splitting between the \(n_{23} = 0\)  and \(n_{23} = 1\)  states induced by switching on the Coulomb blockade on the island. This phase plays no role in the protocol, in fact we expect the superposition in Eq. (REF ) to quickly decohere into a classical equal-probability mixture of \(|0_{23} 0_{14}\rangle \)  and \(|1_{23} 1_{14}\rangle \) . Importantly, the charge on the island is depends on the value of \(n_{23}\) . Let's assume that the charge is \(Q\)  for \(n_{23} = 0\)  and \(Q+1\)  for \(n_{23} = 1\) . At this point, the charge in the island can be measured using charge sensing methods [1]}. The 50% chance for measuring \(Q\)  and \(Q+1\)  respectively is a manifestation of the MBS fusion rule. The fact that the outcome is robust to changes of the pulse strengths and durations, drifts on the ground state charge, and other details of the protocol (within some limits, see Section ) shows the topological nature of the fusion process.
